netic abnormalities, as well as non-genetic causes, including the environment, environmental and gene interaction and metabolic disturbances, with the recurrence risk dependent on the family history and presence or absence of dysmorphic features. Candidate genes for ASD are identified by different means, including cytogenetic abnormalities indicating the location or loss of specific genes) in HC-067047 chemical information individuals with ASD along with overlapping linkage and functional data related to the clinical presentation, with certain chromosome regions identified by genetic linkage using DNA markers that co-inherit with the specific phenotype. A representative example for such an occurrence is the proto-oncogene involved in pathways related to neuronal development and found to be linked to the chromosome 7q31 band, where this gene is located. Decreased activity of the gene promoter was recognized when specific single nucleotide polymorphisms were present in this region by linkage studies. Int. J. Mol. Sci. 2015, 16 6466 However, genetic linkage studies have received only limited success in the study of the genetics of autism. On the other hand, chromosomal microarray analysis using DNA probes disturbed across the genome can be used to detect chromosomal abnormalities at >100-times smaller than seen in high-resolution chromosome studies. Microarray studies have also become the first tier of genetic testing for this patient population and are recommended for all ASD patients. Greater than 20% of studied patients with microarray analysis are found to have submicroscopic deletions or duplications in the genome containing genes that play a role in causing autism. Identification of causative mutations is important to guide treatment selection and to manage PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/1981885 medical co-morbidities, such as risks for seizures, developmental regression or for cancer. Routine cytogenetic studies have shown abnormalities of chromosomes 2, 3, 4, 5, 7, 8, 11, 13, 15, 16, 17, 19, 22 and X, including deletions, duplications, translocations and inversions involving specific chromosome regions where known or candidate genes for ASD are located. These studies further support the role of genetic factors in the causation of this common neurodevelopment disorder. Specifically, cytogenetic abnormalities involving the 15q11q13 region are found in at least 1% of individuals with ASD and include CYFIP1, GABRB3 and UBE3A genes in this chromosome region and most recently the 15q11.2 BP1-BP2 microdeletion syndrome. DNA copy number changes have also shown recurrent small deletions or duplications of the chromosome 16p11.2 band using microarray analysis and the chromosome 15q13.2q13.3 region, whereas copy number changes are noted throughout the genome in individuals with ASD, indicating the presence of multiple candidate genes on every human chromosome. These copy number changes are more often of the deletion type. For idiopathic or non-syndromic autism, the empirical risk for siblings to be similarly affected is between 2% and 8% with an average of 4%. In multiplex families having two or more affected children with autism, the recurrence risk may be as high as 25%, but generally ranges from 13% to 19% if due to single-gene disturbances as the cause, a major focus of this illustrative review. Advances in genetic technology beyond linkage or cytogenetic analysis of affected families with ASD or other complex disorders have led to genome-wide association studies involving hundreds of affected and control i